paper

On-chain electrodynamics of metallic (TMTSF)_2 X salts: Observation of Tomonaga-Luttinger liquid response

arXiv:cond-mat/9801198 · doi:10.1103/PhysRevB.58.1261

Abstract

We have measured the electrodynamic response in the metallic state of three highly anisotropic conductors, (TMTSF)_2 X, where X=PF_6, AsF_6, or ClO_4, and TMTSF is the organic molecule tetramethyltetraselenofulvalene. In all three cases we find dramatic deviations from a simple Drude response. The optical conductivity has two features: a narrow mode at zero frequency, with a small spectral weight, and a mode centered around 200 cm^{-1}, with nearly all of the spectral weight expected for the relevant number of carriers and single particle bandmass. We argue that these features are characteristic of a nearly one-dimensional half- or quarter-filled band with Coulomb correlations, and evaluate the finite energy mode in terms of a one-dimensional Mott insulator. At high frequencies (\hbarω> t_\perp, the transfer integral perpendicular to the chains), the frequency dependence of the optical conductivity σ_1(ω) is in agreement with calculations based on an interacting Tomonaga-Luttinger liquid, and is different from what is expected for an uncorrelated one-dimensional semiconductor. The zero frequency mode shows deviations from a simple Drude response, and can be adequately described with a frequency dependent mass and relaxation rate.

12 pages, 7 figures, RevTeX; minor corrections to text and references; To be published in Phys. Rev. B, 15 July 1998

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